• Photons Flashcards
What speed do electromagnetic waves travel at?
• In a vacuum, all electromagnetic waves travel at the speed of light.
3.00 x 10 ^ 8 m s -1
What is the formula for wavelength?
λ = c ( speed ) / f ( frequency )
What is the formula for frequency?
f = c ( speed ) / λ ( wavelength )
What is the formula for speed?
c = f ( frequency ) x λ ( wavelength )
What does an electromagnetic wave consist of?
Electric wave and a magnetic wave which travel together and vibrate.
What are some features of the vibration of electromagnetic waves?
They travel together and vibrate:
• At right angles to each other, and to the direction in which they are travelling.
• In phase with each other, they are in step.
When can electromagnetic waves be emitted?
Electromagnetic waves are emitted by a charged particle when the particle loses energy.
When can a charged particle lose energy?
- A fast moving electron: Slows down, changes direction or stops.
- An electron in a shell of an atom moves to a different shell of a lower energy, de-excitation
How are electromagnetic waves emitted?
- Short bursts of wave.
- Each burst of waves leaves the source in a different direction.
- Each burst is a packet of electromagnetic waves and is referred to as a photon
What are some features of electromagnetic waves that are emitted?
- Each burst of waves leaves the source in a different direction.
- Each burst is a packet of electromagnetic waves and is referred to as a photon.
What is the formula for photon energy?
E ( photon energy ) = h ( Planck’s constant ) x f ( frequency )
What does a laser beam consist of?
• A laser beam consists of photons of the same frequency.
What is the power of a laser beam ( formula ) ?
- Power of a laser beam is the energy per second transferred by the photons, for a beam consisting of photons of frequency f.
- Power = n ( number of photons passing a fixed point each second ) x h ( Planck’s constant ) x f ( frequency )
- Energy per second.
